1. Field of the Invention
The present invention relates to a pressure switch, which outputs a detection signal when the pressure value of a pressure fluid, as detected by a detector, matches and agrees with a preset pressure value.
2. Description of the Related Art
Heretofore, transporting a workpiece to a predetermined position has been carried out by supplying a negative pressure fluid to a suction transport means made up, for example, from a suction pad, and while the workpiece is attracted under suction to the suction pad. In this case, in order to confirm whether or not the pressure value of the negative pressure fluid supplied to the suction pad reaches and attains a predetermined pressure, whereby it can be confirmed whether or not the workpiece has been reliably attracted under suction, a pressure switch is employed. Generally speaking, such a pressure switch is equipped with a detector made up from a semiconductor pressure sensor, whereby the pressure of the fluid is detected based on a resistance value that changes in accordance with the pressure imposed on the detector. In addition, in the case that the pressure value detected by the detector agrees with a preset pressure value that is set beforehand, it is judged that the workpiece has been attracted under suction and a detection signal is output.
As disclosed in Japanese Laid-Open Patent Publication No. 7-37473, in this type of pressure switch, a vacuum piping is detachably connected through a pipe coupling, to a pressure intake of a main body in which the detector is accommodated. The negative pressure fluid that flows through the vacuum piping is introduced into the main body, whereby the pressure of the negative pressure fluid is detected.
Incidentally, with the aforementioned conventional pressure switch, a pipe joint that connects a main body portion with vacuum piping is formed of a metal material. The pipe joint, which is formed of a metal material, is connected with respect to the main body portion by means of caulking, crimping or the like. However, with the connection structure of this type of pipe joint, since the configuration of the pipe joint is complex, manufacturing costs as well as the time required to manufacture the pipe joint are increased, and hence productivity is lowered.
Further, since it is often the case that the main body in which the detector is accommodated is formed from a resin material, it is necessary to ensure a predetermined connection strength when the metal material pipe joint is connected. For example, although such strength can be increased by disposing a metal washer between the main body portion and the pipe joint, the assembly steps are increased thereby, and along with increasing the number of parts used, assembly variances tend to occur.